Method of manufacturing three-dimensional printed wiring board

ABSTRACT

An efficient method of manufacturing a three-dimensional printed wiring board is provided in which a conductor foil can be reliably heat-fused to the board at a relatively low temperature and the three-dimensional shape such as convex and concave of a mold can be reproduced precisely with no residual stress. 
     The method comprises the steps of providing a filmy insulator comprising a thermoplastic resin composition containing 65-35 wt % of a polyaryl ketone resin having a crystal-melting peak temperature of 260° C. or over, and 35-65 wt % of an amorphous polyetherimide resin, and having a glass transition temperature as measured when the temperature is increased for differential scanning calorie measurement of 150-230° C. superposing a conductor foil on one or both sides of the filmy insulating member, heat-fusing the conductor foil so that the thermoplastic resin composition will satisfy the relation between the crystal-melting calorie Δ Hm and the crystallizing calorie Δ Hc as expressed by the following formula (I), etching the conductor foil to form a conductor circuit, and deforming the printed wiring circuit obtained three-dimensionally. 
     
       
         [(Δ Hm−ΔHc )/Δ Hm   ]≦0.5   (I): 
       
     
     
       
         [(Δ Hm−ΔHc )/Δ Hm   ]≧0.7   (II):

TECHNICAL FIELD OF THE INVENTION

This invention relates to a method of manufacturing a three-dimensionalprinted wiring board, and more particularly a method of manufacturing athree-dimensional printed wiring board having an insulating layer formedfrom a thermoplastic resin.

PRIOR ART

As a rigid board in which a conductor circuit is formed on one or bothsides of a prepreg formed from glass cloth impregnated with an epoxyresin, a three-dimensional printed wiring board formed with a recess forhousing pin and ball grids and LEDs is known. Such three-dimensionalprinted wiring boards are sometimes called PGA (pin-grid arrays) boardsor BGA (ball-grid arrays) boards.

As shown in FIG. 5, in order to manufacture a three-dimensional printedwiring board 12 by forming a recess 11 in a rigid board 10, a male mold13 of a predetermined shape in the form of a round or polygonal columncalled a punching mold is pressed against an intended area for mountingparts on the front surface of a rigid board 10, a female mold 14 calleda die mold is pressed against the back of the rigid board 10, the rigidboard is sandwiched between both molds for hot-pressing to form recesses11 at required places on the rigid board 10 to make the printed wiringboard three-dimensional.

Also, as shown in FIG. 6, another method is known in which cutting workcalled countersinking is done on the front surface of a rigid board 15to form a recess 16 in an intended area for mounting parts to make theprinted wiring board three-dimensional.

As a material for an insulating board of a three-dimensional printedwiring board, a thermoplastic saturated polyester resin is known. Amanufacturing method in which during a step of crystallizing such athermoplastic resin, an insulating board is hot-pressed into apredetermined bent or drawn shape is disclosed in Japanese patentpublications 6-93536 and 7-101772.

Problems the Invention Tackles

But in manufacturing a three-dimensional wiring board using athermoplastic saturated polyester resin for the material of aninsulating board, there is a problem that the insulating board deformsaround a conductor pattern during hot-pressing, and a force (residualstress) that tends to restore the deformed body to the original stateacts on the deformed body. In an extreme case, deformation called“waving” is locally caused.

Also, in manufacturing a conventional three-dimensional printed wiringboard using a glass epoxy resin, control of the degree of crosslinkingof the epoxy resin to the step of hot-press forming is difficult, sothat it is impossible to manufacture satisfactory products inreliability and mass-productivity. Also, for a printed wiring boardreinforced with glass cloth, its use is limited because of lowflexibility.

Also another problem is that if a three-dimensional printed wiring boardfor mounting of parts for which soldering heat resistance is required ora three-dimensional printed wiring board for mere electric wiring issubjected to bending, a bending stress acts on a conductor of copper oraluminum rather than on an insulating board made from a resin that islow in elasticity, so that the conductor is liable to be cut.

Furthermore, with a conventional polyimide-family board material,heat-fusing a conductor foil reliably at a relatively low temperature isnot an easy thing.

An object of this invention is to solve the above-mentioned problems andprovide a strain-free three-dimensional printed wiring board byeliminating residual stresses from the wiring board that has beenhot-pressed to make it three-dimensional in the manufacture ofthree-dimensional printed wiring board using a thermoplastic resin thathas a good heat resistance.

Also, another object of this invention is to make it possible toreliably heat-fuse a conductor foil to a polyimide resin board at arelatively low temperature, and also to provide a method ofmanufacturing a three-dimensional printed wiring board in which anintended three-dimensional shape can be accurately formed byhot-pressing at a relatively low temperature, and to provide athree-dimensional printed wiring board that also has soldering heatresistance and chemical resistance.

A still another object of this invention is to provide athree-dimensional printed wiring board in which conductors are lesslikely to be cut even if bending work is done after a conductor circuithas been formed.

Means to Solve the Problems

In order to solve the above objects, according to this invention, thereis provided a method of manufacturing a three-dimensional printed wiringboard, the method comprising the steps of providing a filmy insulatorcomprising a thermoplastic resin composition containing 65-35 wt % of apolyaryl ketone resin having a crystal-melting peak temperature of 260°C. or over, and 35-65 wt % of an amorphous polyetherimide resin, andhaving a glass transition temperature as measured when the temperatureis increased for differential scanning calorie measurement of 150-230°C., superposing a conductor foil on one or both sides of the filmyinsulator, heat-fusing the conductor foil so that the thermoplasticresin composition will satisfy the relation between the crystal-meltingcalorie Δ Hm and the crystallizing calorie Δ Hc as expressed by thefollowing formula (I), etching the conductor foil to form a conductorcircuit, and deforming the printed wiring circuit obtainedthree-dimensionally.

[(ΔHm−ΔHc)/ΔHm]≦0.5  (I):

If a protective film is provided so as to cover the conductor circuitbefore deforming such a printed wiring board three-dimensionally,bending stress will not concentrate on the conductor circuit, so that itis possible to manufacture a three-dimensional printed wiring boardhaving a conductor circuit which is less likely to be cut.

In order to impart soldering heat resistance to the filmy insulator, inthe above-described method, the printed wiring board formed with aconductor circuit is subjected to heat treatment so that thethermoplastic resin composition will satisfy the relation expressed bythe following formula (II):

 [(ΔHm−ΔHc)/ΔHm]≧0.7  (II):

As the heat treatment, hot-press forming may be employed.

As the conductor foil to be laminated on one or both sides of the filmyinsulator, a conductor foil having its surface roughened is preferablyemployed. As the polyaryl ketone resin, a polyetherether ketone resin ispreferable.

In the method of manufacturing the three-dimensional printed wiringboard of this invention, an insulating layer is formed which comprises afilmy insulator which contains predetermined amounts of a crystallinepolyaryl ketone resin and an amorphous polyether imide resin. Due toexcellent properties of these resins, the insulating layer hasheat-fusability and soldering heat resistance, and also has flexibility,mechanical strength and electrical insulating properties normallyrequired for a printed wiring board.

The thermoplastic resin composition after a conductive foil has beenheat-fused satisfies the relation expressed by the formula (I), has aglass transition temperature of 150-230° C., and the crystal-meltingcalorie Δ Hm and the crystallizing calorie Δ Hc produced bycrystallization while the temperature is being increased satisfies therelation expressed by the formula (I). The progression ofcrystallization of the polyaryl ketone resin due to heating is adjustedwithin a suitable range.

The conductor foil heat-fused to one or both sides of the filmyinsulator is strongly bonded due to the heat-fusability of thethermoplastic resin composition, so that a precision conductor circuitformed by etching the conductor foil is also strongly bonded and lesslikely to peel off. The use of a conductor foil having its surfaceroughened is preferable because the bond strength between the conductorcircuit and the insulating layer increases.

In order to three-dimensionally deform the printed wiring board formedwith a conductor circuit, bending work by external force or hot-pressforming may be employed.

If hot-press forming is carried out to make it three-dimensional, with aprotrusion pressed on a predetermined portion of the surface of theprinted wiring board formed with a conductor circuit, a relatively lowtemperature of 250° C. or lower, usually around 230° C. may be employedfor hot-pressing. At this time, if the relation expressed by the formula(I) is met, the thermoplastic resin will exceed the glass transitiontemperature (Tg), so that it is possible to locally form recesses withhigh accuracy.

The thermoplastic resin composition of the insulating layer of thethree-dimensional printed wiring board thus manufactured exhibitscrystallizability expressed by the above formula (II). This wiring boardhas a sufficient soldering heat resistance to withstand 260° C. Also,the protrusions and recesses of the mold are precisely reproduced, sothat a three-dimensional printed circuit board is manufactured which canreliably accommodate parts to be mounted.

As for the bonding between the filmy insulator and the conductor foil,since they are heat-fused together without any adhesive such as expoxyresin between layers, various properties such as heat resistance,chemical resistance and electrical properties are not governed by theproperties of an adhesive. Thus it is possible to make best use ofvarious excellent properties of the insulating layer.

Also, since the application of an adhesive or cutting work to formrecesses is not needed during the manufacturing steps, the manufacturingprocess is simplified. This provides an efficient manufacturing methodof a three-dimensional printed wiring board.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing manufacturing steps of athree-dimensional printed wiring board of a first embodiment;

FIG. 2 is an explanatory view of bending work for a three-dimensionalprinted wiring board of a second embodiment;

FIG. 3(a) is a partially sectional side view showing a schematicstructure of a cellular phone on which is mounted the three-dimensionalprinted wiring board of the embodiment;

FIG. 3(b) is a partially sectional side view showing a schematicstructure of a cellular phone on which is mounted a conventional printedwiring board;

FIG. 4 is a graph showing the relation between the bending angle ofprinted wiring boards and the cut-wire rate;

FIG. 5 is a schematic view showing a conventional method ofmanufacturing a three-dimensional printed wiring board; and

FIG. 6 is a schematic view showing another conventional manufacturingmethod.

EMBODIMENTS

The first embodiment of the method of manufacturing a three-dimensionalprinted wiring board of this invention will be described with referenceto FIG. 1.

The insulating layer (or filmy insulator) 1 of the printed wiring boardshown in FIG. 1(a) is formed of a thermoplastic resin compositioncontaining 65-35 wt % of a polyaryl ketone resin having acrystal-melting peak temperature of 260° C. or over and 35-65 wt % of anamorphous polyetherimide resin, and having a glass transitiontemperature as measured when the temperature is increased fordifferential scanning calorie measurement of 150-230° C.

In order to manufacture such a printed wiring board, a polyaryl ketoneresin and an amorphous polyether imide resin are added in the aboveratio to prepare a predetermined crystalline thermoplastic filmyinsulator which will be described below.

Then a copper foil is superposed on one or both sides of the filmyinsulator 1 and hot-pressed using e.g. a vacuum hot press to manufacturea double-side-copper-clad laminated board to which copper foils areheat-fused.

In the hot-press step, it is heated so as to exceed the glass transitionpoint of the thermoplastic resin composition but not to exceed thecrystallizing temperature of the thermoplastic resin. While keeping theamorphous state of the thermoplastic resin composition, it is heated toheat-fuse copper foils to both sides of the filmy insulator 1. Thereby,a copper-clad laminated board is formed in which the thermoplastic resincomposition satisfies the relation expressed by the following formula(I). The pressure during pressing for bonding of the copper foils ispreferably 10-100 kgf/cm², more preferably 30-50 kgf/cm².

[(ΔHm−ΔHc)/ΔHm]≦0.5  (I):

Next, conductor circuits 2 are formed by etching the copper foils usingthe subtractive method to obtain a printed wiring board 3 shown in FIG.1(a).

A hard convex plate 4 of stainless steel formed with a protrusion issuperposed on one side (top in the figure) of the printed wiring board3. Also, a hard flat plate 5 of stainless steel is superposed on theother side (bottom in the figure). In this state, it is hot-pressed. Theforming conditions should be such that the thermoplastic resincomposition forming the filmy insulator 1 will satisfy the relationexpressed by the below-described formula (II). In this way, athree-dimensional wiring board 7 formed with a recess 6 of apredetermined shape for mounting parts as shown in FIG. 1(b) ismanufactured.

Hot-press forming for forming the recess 6 at a required area of theprinted wiring board 7 is carried out by heating it to around thecrystal-melting peak temperature (Tc) of the thermoplastic resincomposition (e.g. 220-250° C. ) and accelerating crystallization tomanufacture a three-dimensional printed wiring board that is resistantto soldering heat. The pressure during hot-pressing to make itthree-dimensional is preferably 10-100 kgf/cm² and more preferably 30-50kgf/cm².

Instead of the hard flat plate 5, if a hard convex plate (not shown)formed with a protrusion at a required portion is used, it is possibleto manufacture a three-dimensional printed wiring board formed withrecesses 6 on both sides of the printed wiring board 3.

Also, instead of the hard convex plate 4, if a plate formed withrecesses and protrusions on both sides is used, it is possible to formrecesses and protrusions on both sides of the printed wiring board.

For a printed wiring board formed with conductor circuits, any othermeans for making it three-dimensional than hot-pressing may be employedand later, if soldering heat resistance is required, heat treatment maybe carried out.

The second embodiment shown in FIG. 2 relates to a method ofmanufacturing a three-dimensional printed wiring board by employingknown bending work as a means for making it three-dimensional other thanhot-pressing.

For example, for a printed wiring board 3 formed with conductor circuits2 on one or both sides of insulating layer (filmy insulator) 1, as shownin FIG. 2, [bending work 1] is performed first, and then [bending work2] is performed to increase bent portions, and further [bending work 3]is performed to finish it to a final shape. Then, if soldering heatresistance is required, it is subjected to heat treatment so that thethermoplastic resin composition will satisfy the relation expressed bythe formula (II). If heat treatment is carried out before [bending work1] or [bending work 2], crystallizability of the insulating layer 1 willbe so high that it is difficult to carry out bending work thereafter.

If the application of the three-dimensional wiring board bent to a finalshape is for connection cables or mere electric wiring and thus nosoldering heat resistance is required, the heat treatment that satisfiesthe relation expressed by formula (II) may be omitted.

With a conventional cellular phone as shown in FIG. 3(b), there is aproblem that since a printed wiring plate is difficult to bend, unusedspace remains in the back of the display 8. But as shown in FIG. 3(a), abent three-dimensional printed wiring board can be arranged along adisplay 8 inclined in a thin cellular phone and a battery housing 9.Such a bent three-dimensional printed wiring board can be set in asmall-volume space in which even a flexible printed wiring board cannotbe housed.

Also, a protective film formed before the printed wiring board isthree-dimensionally deformed may be formed from the same resincomposition as the filmy insulator in which polyaryl ketone andamorphous polyether imide resins are mixed at a predetermined rate, ormay be of the same material as an ordinary cover film for a printedwiring board.

With a printed wiring board provided with a cover film, stress on theconductor circuits when the printed wiring board is in a bent state isrelaxed. Thus cutting of wires is less likely to occur.

The test results shown in FIG. 4 show the cut-wire rates for a board{circle around (1)} having no protective film covering conductorcircuits (copper pattern only), for a board {circle around (2)} formedwith an ordinary solder-resist (solder-resist), and for a board {circlearound (3)} having a protective film of the same resin composition asthe insulating layer (cover film), when single-faced boards formed withthe same circuit patterns of the same thickness were bent to 30°, 60°and 90° under the heat-press conditions of 10 minutes at 240° C.

As will be apparent from FIG. 4, while in the case of wiring boards{circle around (1)}, {circle around (2)}, for 60% or more of the printedwiring boards, wires were cut at bending at 60° or over, for most of theprinted wiring boards {circle around (3)} having a protective film,wires did not break until 90°.

From these results, apparently the printed wiring boards provided with aprotective film covering the conductor circuits have an advantage ofpreventing cutting of wires by reducing stress on wiring deformed bybending.

Next, description will be made about thermal property of the filmyinsulator after heat fusion of the conductive foil, which is animportant control factor in the present invention. This thermal propertyis that the relation between the crystal-melting calorie Δ Hm and thecrystallizing calorie Δ Hc produced by crystallization while thetemperature is increasing satisfies the relation expressed by theformula (I).

Such a thermal property can be calculated by the above formula frommeasured values of two heats of transition that appear on DSC curveswhen the temperature is increased for differential scanning caloriemeasurement under JIS K7121 and K7122, crystal-melting calorie Δ Hm(J/g) and crystallizing calorie Δ Hc (J/g).

While the value of the formula (I) depends on the kind and molecularweight of the material polymers and the content ratio of thecomposition, forming and working conditions of the filmy insulator havea large influence thereon. That is to say, it is possible to reduce thevalue of the above formula by quickly cooling the material polymer afterthe polymer has been melted to form into a film. Also, these values canbe controlled by adjusting the heat history applied during each step.Heat history herein used means the temperature of the filmy insulatorand the time during which it was at that temperature. The higher thetemperature, the greater the value tends to be.

The relation expressed in formula (I) is based on measurement beforehot-pressing for the blank board for printed wiring after a conductivefilm has been heat-fused to at least one side of the filmy insulator inthe steps of manufacturing the printed wiring board.

If the value expressed by formula (I) is higher than 0.5 before heattreatment such as hot pressing, since the thermoplastic resincomposition is already in a high crystallizability, the shapes of therecesses formed by hot pressing will not conform to the mold shapes.Thus, it becomes necessary to carry out heat treatment such as hotpressing at a high temperature exceeding 250° C., so that themanufacturing efficiency lowers.

The thermal property that the filmy insulator has soldering heatresistance is to satisfy the relation of the formula (II) afterformation of recesses. This is because it is considered that if thevalue of formula (II) is lower than 0.7, crystallization of theinsulating layer is not sufficient to maintain soldering heat resistance(usually 260° C.

[(ΔHm−ΔHc)/ΔHm]≧0.7  (II):

The filmy insulator is usually one having a thickness of 25-300 μm, e.g.25 μm, 50 μm, 100 μm or 200 μm. As its manufacturing method, a knownfilm-forming method such as extrusion casting using a T-die or acalender method can be employed. But the method is not limited. From aviewpoint of film-formability and stable productivity, it is preferableto employ the extrusion casting using a T-die. The forming temperaturein the extrusion casting is adjusted depending on the flow andfilm-forming properties of the composition. But it is above the meltingpoint of the composition and less than 430° C.

In this invention, the polyaryl ketone resin, which is the firstcomponent forming the filmy insulator, is a thermoplastic resincontaining an aromatic nucleus bond, ether bond and ketone bond as itsstructural units. That is to say, it is a heat-resistant, crystallinepolymer having a combined structure of phenyl ketone and phenyl ether.

As representative examples of polyaryl ketone resin, there are polyetherketone, polyether-ether ketone, polyether ketone-ketone, etc. In thisinvention, polyether-ether ketone expressed by the chemical formula 1 isthe most preferable.

The amorphoyuse polyether imide resin, which is the second componentforming the filmy insulator, is an amorphous thermoplastic resincontaining an aromatic nucleus bond, ether bond and imide bond as itsstructural units. In this invention, the polyether imide resin expressedby the chemical formula 2 can be used.

The filmy insulator used in this invention comprises a composition inwhich the above two kinds of thermoplastic resins are blended at apredetermined ratio. The thermoplastic resin composition comprises 65-35wt % of a polyaryl ketone resin having a crystal-melting peaktemperature of 260° C. or over, and 35-65 wt % of an amorphous polyetherimide resin, and has a glass transition temperature as measured when thetemperature is increased for differential scanning calorie measurementof 150-230° C.

The reason why the blend ratio is limited to the above range is becauseif the polyaryl ketone resin is added in a larger amount than 65 wt %,or if the content of the polyether imide resin is less than 35 wt %, thecrystallizing speed of the composition would become too fast, so thatthe heat-fusability with the conductive foil lowers. If the crystallinepolyaryl ketone resin is less than 35 wt %, or the amorphous polyetherimide resin exceeds 65 wt %, the crystallinity of the composition woulddecrease, so that the soldering heat resistance decreases even if thecrystal-melting peak temperature is 260° C. or over.

To the resin composition forming the filmy insulator used in thisinvention, other additives such as resins may be added. As specificexamples thereof, heat stabilizers, ultraviolet absorbers, lightstabilizers, colorants, lubricants, flame retardants, inorganic fillers,etc can be cited. Also, to the surface of the filmy insulator, embossingor corona treatment may be applied to improve handling property.

As the conductive foil used in this invention, a metallic foil having athickness of 8-70 μm such as copper, gold, silver, aluminum, nickel andtin can be cited. Among them, a copper foil having its surface subjectedto chemical conversion coating such as black oxiding is preferable. Asthe conductor foil, it is preferable to use one having its contactsurface (superposed surface) with the filmy insulator roughenedbeforehand chemically or mechanically. As an example of the conductorfoil having its surface roughened, a roughened copper foil can be namedwhich is electrochemically treated when an electrolytic copper foil ismanufactured.

EXAMPLES AND COMPARATIVE EXAMPLES

Description is made hereinbelow about the manufacturing examples 1-3 offilmy insulator that satisfy the conditions for the filmy insulator ofthis invention, and comparative examples 1, 2 for comparison therewith,and their physical properties.

Manufacturing Example 1 of Filmy Insulating Member

60 wt % of polyether-ether ketone resin (PEEK 381G, made by Victolex)(in the following description and Tables 1 and 2, it is abbreviated toPEEK) and 40 wt % of polyether imide resin (Ultem-1000 made by GeneralElectric)(in the following description and Tables 1 and 2, it isabbreviated to PEI) were dry-blended. This mixed composition was formedby extrusion into a filmy insulator having a thickness of 25 μm.

Manufacturing Example 2

Except that the blend rate of the mixed composition was 40 wt % of PEEKand 60 wt % of PEI, a filmy insulator was manufactured in the samemanner as in the Example 1.

Manufacturing Example 3

Except that the blend rate of the mixed composition was 30 wt % of PEEKand 70 wt % of PEI, a filmy insulator was manufactured in the samemanner as in Example 1.

Reference Examples 1 and 2

Except that the blend rate of the mixed composition was 100 wt % of PEEK(reference example 1) and 100 wt % of PEI (reference example 2), a filmyinsulator was manufactured in the same manner as in Example 1.

In order to examine the physical properties of the filmy insulatorobtained in the Manufacturing Examples and Comparative Examples, for theitems (1) and (2) shown below, values were measured or calculated frommeasured values. These results are shown in Table 1.

(1) Glass Transition Temperature (°C.), Crystallizing Temperature (°C.),Crystal-melting Peak Temperature (°C.)

Under JIS K7121, using 10 mg of specimens, the above temperatures werecalculated from a thermograph when the temperature was increased withthe heating speed of 10° C. per minute using DSC-7 made by Perkin Elmer.

(ΔHm−ΔHc)/ΔHm  (2):

Under JIS K7122, using 10 mg of specimens, the crystal-melting calorie ΔHm (J/g) and the crystallizing calorie Δ Hc (J/g) were calculated from athermograph when the temperature was increased with the heating speed of10° C. per minute using DSC-7 made by Perkin Elmer. Then the value ofthe above formula was calculated.

EXAMPLE 1

Electrolytic copper foils having a thickness of 12 μm and having theirsurface electrochemically roughened were superposed on both sides of thefilmy insulator having a thickness of 25 μm obtained in ManufacturingExample 1, and heat-fused in a vacuum atmosphere of 760 mmHg, pressingtemperature of 220° C., press pressure of 30 kg/cm², and pressing timeof 20 minutes to manufacture a double-sided copper-clad laminated board.

For the filmy insulator of the laminated board thus manufactured,measurements of item (2) were carried out by the same method asdescribed above. The value of the formula is shown in Table 2.

Also, for the laminated board thus manufactured, the bond strength wasmeasured by the method (3) described below. The result is also shown inTable 2.

Next, a printed wiring board was manufactured in which a circuit patternwas formed by the subtractive method on the copper-clad laminated boardthus obtained and conductive circuits were formed by etching.

The soldering heat resistance of the printed wiring board obtained wasmeasured by the test method of the method (4) below. The result is alsoshown in Table 2.

Also existence or non-existence of ply separation was examined by themethod (5) below. The result is shown in Table 2.

(3) Bond Strength

Under JIS C6481 (ordinary-state peel strength), peel strengths of thecopper foil of the printed wiring blank board was measured and theiraverage value was expressed in kgf/10 cm.

(4) Soldering Heat Resistance

Under JIS C6481 (soldering heat resistance in ordinary-state), after itwas floated on a solder bath of 260° C. for 10 seconds with the copperfoil side of the printed wiring blank board of the test piece in contactwith the solder bath, it was taken out of the bath and let to cool toroom temperature. Existence or non-existence of blistered or peeledportions were visually observed to evaluate if it was good or no good.(5) FPC was buried in an epoxy resin. Specimens for observing theirsections were prepared by a precision cutting machine, and the cutsurfaces were observed under a scanning electron microscope (SEM) toevaluate existence or non-existence of ply separation between the filmyinsulator and the conductive circuit of copper foil.

A convex plate 4 of stainless steel formed with a disk-shaped protrusionhaving a height of 25 μm as shown in FIG. 1(a) was superposed on the topsurface of the printed wiring board thus obtained, and with a flatsurface of a flat plate 5 of stainless steel pressed on the underside ofthe printed wiring board, it was hot-pressed at about 230° C. underpressure of 30 kgf/cm² so that the insulating layer 1 comprising thefilmy insulator will be a thermoplastic resin composition that satisfiesthe relation expressed by the formula (II) to manufacture athree-dimensional wiring board.

EXAMPLE 2

Except that Manufacturing Example 2 was used as the filmy insulator andthe press temperature when manufacturing the copper-clad laminated boardwas changed to 240° C. and the press time was changed to 30 minutes, aprinted wiring board was manufactured in a similar manner to Example 1.The evaluations of tests (3)-(5) are shown in Table 2. Further, athree-dimensional printed wiring board was manufactured in a similarmanner to Example 1.

Comparative Example 1

Except that the press temperature was changed to 230° C. and the presstime was changed to 10 minutes, a printed wiring board was manufacturedin a similar manner to Example 2. The evaluations of tests (3)-(5) areshown in Table 2. Further, a three-dimensional printed wiring board wasmanufactured in a similar manner to Example 1.

Comparative Example 2

Except that Manufacturing Example 3 was used as the filmy insulator andthe press temperature was changed to 240° C. and the press time waschanged to 20 minutes, a printed wiring board was manufactured in asimilar manner to Example 1. The evaluations of tests (3)-(5) are shownin Table 2. Further, a three-dimensional printed wiring board wasmanufactured in a similar manner to Example 1.

On the three-dimensional printed wiring board of Example 1, theprotruding and recessed shape of the mold was precisely reproduced sothat parts could be reliably received in the recesses. Further the bondstrength of the copper-clad laminated board was, as will be apparentfrom the results of Table 2, as good as 1.6 kgf/10 cm. As for theresults of soldering heat resistance test, no blisters and peeling wereobserved in the board at all. Also, in the SEM observation of the FPCafter formation of conductor circuits, no ply separation was observed atall.

On the three-dimensional printed wiring board of Example 2 too, theconvex and concave shape of the mold was precisely reproduced and athree-dimensional printed wiring board was obtained in which the partswere reliably accommodated in the recesses. Also, the bond strength ofthe laminated board having both sides copper-clad was as good as 1.4kgf/10 cm, and the result of the soldering heat resistance test was goodtoo. Also, in the SEM observation after formation of conductive circuitsby etching, no ply separation was observed at all.

In contrast, for Comparative Examples 1 and 2, on three-dimensionalprinted wiring board, the convex and concave shape of the mold wasalmost precisely reproduced, and in Comparative Example 1, there was agood adhesion between layers in the SEM observation. But for thesoldering heat resistance, blisters and peeling on the board wereobserved and the results were no good.

Also, for the printed wiring board of Comparative Example 2, the bondstrength of the laminated board having both sides copper-clad was as badas 0.2 kgf/10 cm. After formation of conductive circuits by etching,copper foil at the circuit portion peeled.

Effect of the Invention

In the method of manufacturing a three-dimensional printed wiring boardof this invention, as described above, because a conductor foil issuperposed on the surface of a filmy insulator comprising apredetermined thermoplastic resin composition and is heat-fused underpredetermined conditions to adjust the crystal state of thethermoplastic resin composition, the conductor foil can be reliablyheat-fused to the polyimide resin-family board at a relatively lowtemperature. Also, no residual stress remains in the wiring board thathas been deformed by bending or hot-pressed to make itthree-dimensional. Thus, there is an advantage that a strain-freethree-dimensional wiring board can be manufactured.

In particular, in a case where a printed wiring board is hot-pressedwith a mold pressed against a required portion, hot-press forming ispossible in which the convex and concave shape of the mold is preciselyreproduced at a relatively low temperature of less than 250° C.,preferably around 230° C. Thus, it is possible to manufacture athree-dimensional printed wiring board in which the bond strengthbetween the insulating layer and the conductor circuits is good and noresidual stress remains in the wiring board after formation so thatthere is no strain in the board.

In the case in which a printed wiring board formed with conductorcircuits is subjected to predetermined heat treatment, it is possible toefficiently manufacture a three-dimensional wiring board which has asufficient soldering heat resistance to withstand 260° C., and whichalso has good chemical resistance and electrical properties.

Furthermore, in the manufacturing method of a three-dimensional wiringboard in which a protective film covering the conductor circuits isformed, even if bending work is carried out after formation of theconductor circuits, the conductors are less likely to suffer cutting.

TABLE 1 Number Ref. manufacturing example Ref. Property ex. 1 1 2 3 ex.2 Content PEEK 100 60 40 30 0 (wt %) PEI 0 40 60 70 100 (1) Glasstransition temp. 139 166 186 192 216 (° C.) Crystallization temp. 170214 248 249 — (° C.) Crystal-melt peak 343 342 341 340 — temp. (° C.)(2) ΔHm (J/g) 48 30.4 15.7 14.4 — ΔHc (J/g) 29 22.5 15.3 13.8 —(ΔHm-ΔHc)/ΔHm 0.40 0.26 0.03 0.04 —

TABLE 2 Number Example Com. example Property 1 2 1 2 Content PEEK 60 4040 30 (wt %) PEI 40 60 60 70 hot-press temp. (° C.) 220 240 230 240hot-press time (min.) 20 30 10 20 (2) (ΔHm-ΔHc)/ΔHm 0.97 0.94 0.61 0.65(3) Bond strength (Kgf/10 cm) 1.6 1.4 0.8 0.2 (4) Soldering heatresistance good good bad bad (5) Ply peeling in SEM no no no yes

What is claimed is:
 1. A method of manufacturing a three-dimensionalprinted wiring board, said method comprising the steps of providing afilmy insulator comprising a thermoplastic resin composition containing65-35 wt % of a polyaryl ketone resin having a crystal-melting peaktemperature of 260° C. or over, and 35-65 wt % of an amorphouspolyetherimide resin, and having a glass transition temperature asmeasured when the temperature is increased for differential scanningcalorie measurement of 150-230° C., superposing a conductor foil on oneor both sides of said filmy insulator, heat-fusing said conductor foilso that said thermoplastic resin composition will satisfy the relationbetween the crystal-melting calorie Δ Hm and the crystallizing calorie ΔHc as expressed ((ΔHm−ΔHc)/ΔHm)≦0.5, etching said conductor foil to forma conductor circuit, and deforming the printed wiring circuit obtainedthree-dimensionally.
 2. The method of manufacturing a three-dimensionalprinted wiring board as claimed in claim 1 wherein a protective film isprovided to cover said conductor circuit before deforming said printedwiring board to make it three-dimensional.
 3. The method ofmanufacturing a three-dimensional printed wiring board as claimed inclaim 1, wherein the printed wiring board formed with the conductorcircuit is subjected to heat treatment so that said thermoplastic resincomposition will satisfy the relation expressed by the following formula(II): [(ΔHm−ΔHc)/ΔHm]≧0.7  (II):
 4. The method of manufacturing athree-dimensional printed wiring board as claimed in claim 3 whereinsaid heat treatment is hot-press forming.
 5. The method of manufacturinga three-dimensional printed wiring board as claimed in claim 1 whereinsaid conductor foil laminated on one or both sides of said filmyinsulator has its surface roughened.
 6. The method of manufacturing athree-dimensional printed wiring board as claimed in claim 1 whereinsaid polyaryl ketone resin is a polyetherether ketone resin.